Electrical System: Battery

Motorcycle batteries are typically not "repairable," per se, but some preventive maintenance will make them last much longer. For those of you who, like the majority of riders, experience at least one season where riding is at least discouragingly uncomfortable (if not downright dangerous), a battery trickle charger is a vital purchase. A charger with 1- or 1.5-amp capacity is quite sufficient. Don't spend lots of extra money on a fast charger, because the high current can damage batteries in some cases. I got a 1.5 amp 6/12-Volt (switchable) charger from Auto Zone for $25 that seems perfectly sufficient for this purpose. I figure spending $25 once is cheap insurance against spending $30-40 every year to replace the battery.

It's very likely that you'll experience a need for a jump-start at least once. Forget everything you've heard about jumping motorcycles from cars. Most of it isn't true. Instead, read up on what the Texas VFR Garage has to say, as well as Tip 104 and Tip 73 from Motorcycle Tips and Tricks.

Electrical System: Ignition Coil

One of the worst designs of the KZ400 is its ignition coil. The spark plug wires are moulded into the coil, making them extremely difficult to replace or repair, as I found out recently when I went out for a quick trip to the bank and started up the bike, only to find it was running solely on its left cylinder.

Fortunately, coils are a fairly generic item. Any dual-output coil of approximately 4 ohms primary resistance — or a coil of lesser resistance combined with a ballast resistor — should work as a replacement. You should be familiar with the term "UJM," short for "Universal Japanese Motorcycle," because it applies extremely well to the 4-stroke Japanese bikes from about 1975 to the mid-1980s.

I found an "unknown" TEC coil on eBay; by googling the model number of the coil, I was able to determine it came from a Honda CB1000 of the late-1970s vintage. I took a $6 gamble and it paid off — the coil was identical in size, mounting points, and electrical specs to the coil it replaced. I simply had to crimp new connectors onto the old coil wires and buy new spark plug wires. Sneaky trick for spark plug wires: buy a pre-made wire twice as long as you need with two 90-degree plug caps on it. I got mine from the local auto parts shop. Cut it in half in the middle and you have your two plug wires, ready for insertion into the screw-on retainer caps on the coil.

Electrical System: Spark Plugs

The importance of a good — and properly fitted — spark plug is often underestimated by people new to the world of gasoline engines. NGK seems to be the brand Kawasaki chose as its OE supplier, and with good reason: NGK make quality plugs.

If you prefer another brand (Denso seems to make a good iridium plug that matches the B8ES NGK cross-reference, whereas NGK doesn't seem to make an iridium plug in that style), this spark plug manufacturer cross-reference will help you find what you want.

And in case you ever wanted to know what those numbering codes mean, here are explanations for NGK, Denso, and Champion. Finally, whilst I normally don't like linking to commercial sites as informational sources, Sparkplugs.com has an excellent search engine with built-in cross-referencing for all types of plugs.

Fuel System: Carburetors

Carburetors are amazing little devices. They're entirely mechanical, yet they manage (when properly tuned) to deliver a nearly-perfect mixture of air and fuel to the cylinders at the entire range of engine speeds. The key is getting them — and keeping them — properly tuned in the first place.

As anyone who's ever worked on an older bike that sat for any period of time knows, the carbs are the first things to get gunky. Most owners don't follow the Dick Shilts mantra: "Proper Preparation Prevents Poor Performance." Properly prepping the bike for storage will prevent nearly all major carb issues. When I got my bike, the P.O. (that's "previous owner" for you non-biker types or newbies to the hobby), of course, had let it sit for four years with gas in it.

This is NOT a good idea. DO NOT do this with your bike. DO NOT let your friends do this with their bikes.

DO, however, jump at the chance to buy a bike very cheaply because the owner thinks it runs poorly now but ran fine when he put it in storage. This is almost guaranteed to be a carburetor issue, and should be fixable for under $100 if you're willing to do the work yourself. But I digress.

Anyway, the first thing I did was pull the carbs off the bike (a real procedure in itself) and completely disassemble them. I then ordered two carb kits to replace every piece of rubber in the carbs except for the pilot jet passage plugs. I removed all the old rubber, set it aside, and soaked every single jet in carb cleaner for two days. I then ran thin wires through all of them to make sure no bits were stuck in the jets themselves, and let everything go through an ultrasonic cleaner for half an hour. That got every last bit of gummed gasoline and solid particles out of the jets. I also blew carb cleaner through all the passages I could find in the carb bodies while the jets were out. (NEVER blow carb cleaner or compressed air through an assembled carburetor as it can damage the jets.) I reassembled everything and the bike wouldn't allow any throttle. It would idle, roughly, but it would die when I gave it gas.

Long story short, it turns out I had installed the main jet keepers upside-down, so they were doing exactly NOTHING to keep the main jets in place. Fixed that and things were hunky-dory.

I should probably mention at this point that I was fortunate enough to get the carb kits on closeout from Cycle ReCycle in Indianapolis; kits for the '76 and earlier carbs appear no longer to be available anywhere. However, the float needles are the only true specialty item in the kits. Exact (or very similar) replacements for all the O-rings are either commercially available or can be made quite easily from a length of Buna-N rubber cord of the proper diameter. The plugs for the pilot jet passages are fairly simple items as well. I didn't replace mine because they were in fine shape, but cutting a plug of rubber to fit the passage would be a very simple matter if an exact replacement could not be found.

Once the carbs are clean and full of fresh rubber, if you expect to get halfway decent performance out of them, you'll need to synchronise them. This is perhaps the worst part of properly tuning multi-carburetor engines, but it doesn't need to be expensive. The $1.55 carb sync tool (only useful for 2-carb setups, unfortunately, though I believe the design could be modified for a 4-carb bike) will help you to sync your carbs properly at a very budget-minded price. More good carb sync info can be found at Powerchutes and KZrider.

Fuel System: Fuel Tank

With 20+ years on these bikes, it's very likely at least part of that time was spent outdoors. Because weather tends to deteriorate bikes, and because people tend to be lazy about maintenance, a lot of bikes aren't properly winterised and suffer rusty tanks as a result of moisture getting into the system. The rust then flakes off into the petcock and fuel system, causing all sorts of problems down the road.

A good idea on any older bike is to coat the inside of the fuel tank with a sealant in order to nip these problems in the bud and prevent any rusting in the future. The sealant with perhaps the best reputation among DIY repair folks is POR-15, which is really an entire company specialising in restoration products for vehicles of all types. The Utility and Cycle Tank Repair Kit, which uses their US Standard Fuel Tank Sealer, is what I'll be ordering this winter, and I'll update this page with my experience when I finish the project. While you're at it, get their free catalog. You won't be disappointed.

Fuel System: Petcock

A faulty petcock will, at best, supply fuel irregularly, and at worst, either fail to supply fuel at all or leak gasoline all over the place, which is particularly hazardous when the engine is hot.

My petcock was full of rust (see the bit about fuel tanks above) and needed a good cleaning. During the cleaning, I discovered that the diaphragm behind the petcock lever was thoroughly worn from 20-odd years of use and needed to be replaced. Both O-rings were also faulty. The O-rings were all of 75 cents from my local True Value hardware store, but I'm still searching for a petcock diaphragm. Kawasaki no longer makes the petcock diaphragm for the 1976 and earlier petcocks, so I'm planning on making my own this winter. More info on that when I get around to it. Meanwhile, here are twothreads on petcock issues for your perusal.

Finally, one more tip. If the threads on either the petcock retaining bolts or the petcock bung itself leak at all — and they can, albeit rarely — use some PTFE (Teflon™) tape on the threads and they won't leak any more.

Other Repairs: Tires

A piece of advice: find some tires you want, then do plenty of shopping around online. Then get Dennis Kirk to match the price and get them there, if DK has 'em in stock. If they don't, your next stops should be MAW Online and Ron Ayers Motorsports. Both have pretty good prices and occasionally have stock that DK doesn't have.

Avoid Cheng Shin or Kenda tires unless you're just wanting to put on some cheap tires to sell the bike. I have a pair of Dunlops (100/90-18 front, 110/90-18 rear) here waiting for some garage time. I'll post experiences in mounting/balancing/etc. when I get them. Probably another winter project...

Other Repairs: Handlebars

The stock handlebars were bent when I bought the bike. It wasn't bad, but it was noticeable and mildly annoying. After a season of riding, I find that I prefer a more forward-leaning riding position anyway, so the stock bars got tossed for some "Superbike"-style bars from Cycle ReCycle. At $25 shipped for brand-new chrome bars, I think it was a pretty good deal.

The handlebar swap itself was fairly painless; I simply had to loosen every clamp on the bars and undo the throttle and clutch cables. The grips — I kept the stock grips for now — were a bit trickier. I had to do some prying with a thin screwdriver and some WD-40 to get the grips off the old bars. Once I wiped out all the old lubricant (don't want your grips spinning on the bar!), putting the grips on the new bars was a piece of cake.

What isn't going to be painless is the height difference between the old and new bars. All my control cables are now about five inches too long, and so is my brake line. I had sort of planned on re-doing the brake lines anyway, so that doesn't bother me too much, but I'm not looking forward to either replacing a set of perfectly good cables or to taking the trouble to track down exactly the right length.

Other Repairs: Disc Brakes

Bleeding down and flushing hydraulic disc brakes is a giant pain in the arse, but it needs to be done. I recommend a few things:

Get a bleeder screw with a built-in check valve. This is probably the most important part.

Have a wet cloth and plenty of water available.

Buy brake fluid in one-quart or one-litre bottles. Running out of fluid in the middle of bleeding is a real pain.

Do the bleeding on your lawn, or out in a parking lot. Brake fluid will make nasty spots on blacktop driveways if left in puddles. Dilute any spilled fluid with lots of water and it'll go away; brake fluid is chemically very similar to antifreeze, which is fairly harmless.

Put the bike on its centrestand if possible; this is a lot easier to do if your front wheel (and thus handlebars) is fairly straight and the bike isn't leaning over. Your master cylinder (hereafter abbreviated m/c) will probably be full of gunk (technical term). Get as much of the gunk as you can out with a rag or your finger before you start flushing the brakes. With the lid off your m/c, fill it about 2/3 full with fresh fluid. Attach a clear hose (so you can see air coming out) to your check valve-equipped bleeder screw on the front caliper and immerse the other end of the hose in a glass jar containing a few tablespoons of brake fluid.

Work your brake lever back and forth, never allowing the brake fluid level in the m/c to drop below 1/4th full, until the fluid coming out of the bleeder hose looks like the new fluid you've been pouring into the m/c. When this happens, tighten up the bleeder screw and then re-fill the m/c as needed to bring the level up to the bottom of the rubber diaphragm. Replace your m/c cap and test the front brake. It should feel firm, not spongy. If it's spongy, there's still air in the system. You may need to loosen the caliper, rotate it so the bleeder screw is at the top of the caliper (surprisingly enough, they aren't always designed this way), open the bleeder, and pump out the rest of the air bubbles.